Hello all this is Dr Alsup and it is the most wonderful time of the year, time to talk
musculoskeletal anatomy. Now as you've likely heard and as you can kind of just observe there is a lot
of anatomy when discussing the musculoskeletal system. Think of how many bones joints and muscles
there are in the body. Our discussions will be focused on the appendages so the upper and the
lower limbs and we're going to start with the basics of the bones and joints of the upper limb.
And there's a lot of material in this learning objective as we are going to introduce all of
the bones and the major joints of the upper limb. Do understand that we will discuss these in a bit
more detail as we move through the week so here I am really hoping to just get used to the terms, as
in the names of the bones and the joints and get a basic understanding of where these are located.
Fortunately as well the basic organization of the upper and lower limbs are similar
with the single bone in the true most proximal segment two bones in the intermediate segment
and numerous smaller bones associated with the distal most portion so the wrist and the hand
as well as the ankle and the foot. But before we get started I want to do a quick terminology quiz.
Do you recall what the term proximal means? Hopefully you're landing on
proximal means towards the trunk or point of origin, so hopefully that jogs your memory as
to what distal means. Distal means away from the trunk or point of origin. We will be using these
terms a lot throughout our MSK discussions as in the proximal part of a bone which is going
to be the part that's closer to the trunk or the distal portion of the bone so away from the trunk.
So we will begin with the proximal bones which together are referred to as the pectoral girdle.
And these bones serve to connect the trunk or the axial skeleton to the upper limb, so they're kind
of in an intermediate place between the trunk and the upper limbs but we're still going to
to mention them here. The clavicle which is colloquially referred to as the collarbone
is located near the root of the neck. We saw it quite a bit when we were dissecting in this area.
And it is firmly articulated with the trunk at the sternum so at this sternoclavicular joint right
here. It will also articulate with the acromion of the scapula so that kind of lateral most extension
at the acromioclavicular or AC joint. Remember you can palpate the clavicle for almost
its entire length and where it ends laterally means you are at the acromioclavicular joint.
The scapula sometimes referred to as the shoulder blade will distally articulate with
the head of the humerus to form the glenohumeral joint, more commonly referred to as the shoulder joint
which has the distinction of being the most freely movable joint in the body.
Let's think a little more about the humerus. This is the only bone of the arm region and it's
also the longest bone of the upper limb. It is as mentioned will articulate with the scapula at the
glenohumeral joint and distally it will articulate with both the radius as well as the ulna or
those forearm bones so the humeroulnar joint is typically considered the true elbow joint but the
humeroradial is within that same complex of the elbow joint so closely associated with the elbow.
Speaking of the radius and ulna let's get to know them a little bit more. The ulna is going to be
the more medial of the forearm bones and will play a big role in movements at the elbow joint.
The radius is, so this is medial and this is lateral, so the radius is the more lateral of the
forearm bones and will play a big role in terms of the wrist joint or the radiocarpal joint in fact
the ulna does not articulate with the carpal bones at all it doesn't quite reach that area it's
more proximal and is going to be its largest component. The radius and ulna will articulate
with one another in three separate areas so forming three separate radial ulnar joints.
There is the proximal radio-ulnar as well as the distal radio-ulnar. Which play these joints
play a big role in terms of the actions pronation and supination, and there's also a joint that joins
the shafts or the bodies of the radius and ulna at the interosseous membrane so often referred
to as the radio-ulnar syndesmosis because this is actually example of a fibrous joint.
Now moving to the wrist and hand and this is where the bone count and joint count really
increases significantly. The carpal bones can also be thought of as the wrist bones
and these are examples of short bones. There are eight carpal bones in all per hand. There is four
in the proximal row, so this is the proximal and four in the distal row
of carpal bones. So that proximal row is going to articulate with the distal radius at the
radiocarpal joint or wrist joint and well all of these three right here the pisiform actually
doesn't articulate with the radius this is an example of a pisiform or excuse me a sesamoid bone.
One bone I do want you to be able to identify is the scaphoid which is the lateral
most carpal bone in the proximal row. And the reason that we typically discuss the scaphoid
is because it is the most frequently fractured carpal bone. And when fractured due to its tenuous
and retrograde blood flow avascular necrosis is possible associated with this bone.
Any joint so any time that these bones articulate with one another so a carpal bone with another
carpal bone those are referred to as intercarpal joints so that will be kind of throughout this
complex. The distal row of carpal bones will articulate with the metacarpals which are
these bones right here or the bones in the general palm region at the carpometacarpal or CMC joints.
There are five metacarpals and they are literally numbered with the first
metacarpal being the lateral most so make sure you're thinking in terms of anatomical position,
with the palms facing forward or anteriorly. And so that first metacarpal is associated with the thumb
and we know the thumb is lateral and anatomical position. And then it moves in order from there
with two three four and five, five being associated with the fifth digit or the pinky finger.
Distally the metacarpals will articulate with the proximal phalanges at the metacarpophalangeal
joints which are a really long name so very often you just see it abbreviated
as the MP joints or the MCP joints. And now to everyone's favorite the phalanges. These are the
bones of the digits and there are three rows of phalanges. You have the proximal phalanges
of which there are five, the intermediate phalanges of which
there are only four, so no intermediate phalanges associated with the first digit.
And then again there are five distal phalanges so these are by far the smallest of the phalanges.
The joints between the proximal and the intermediate phalanges of digits
2 through 5 are referred to as the proximal interphalangeal or the PIP joints
and the joints between the intermediate phalanges and the distal phalanges
are referred to as the distal interphalangeal or DIP joints. And since there is no intermediate
phalanges associated with the first digit the joint between the proximal and the distal phalange
is just referred to as the IP or the interphalangeal joint.
Excellent so we have already reviewed all of the bones and major joints of the upper limb.
Not too shabby for the first learning objective in musculoskeletal anatomy. And hopefully you can
use this handy dandy summary slide to refer back to and study. As mentioned we will talk
details about these bones and joints as we continue to explore musculoskeletal.
But now we should at least be familiar with the names and general locations.
So you could keep coming back to this slide just as kind of a point
of review. All right thank you for your time and attention here and as always if you have any
questions please feel free to reach out to myself or any of my anatomy colleagues. Have a great day